invasive fish can seriously threaten the conservation of some of these species. This
can also be the case of other species with wider distribution, either because their
distribution is restricted to high mountain areas (fish introductions in mountain
areas are a global threat; Hulme et al. 2009) or because a synergy with other
stressors also affecting the remaining distribution area (e.g. Davis et al. 2010; Ban
et al. 2014; Matthaei et al. 2010). Recent genetic studies have also shown that for
other species with wide geographic distribution there are genetically differentiated
lineages in high mountain areas (Ventura et al. 2014; e.g. Bellati et al. 2014), that
might also be at risk of disappearance.
To what extent this substantial habitat loss is indeed affecting the survival of
some of the native species is not well known for most of them. Theoretical studies
point out that species-specific empirical studies are required with great urgency. If
the decrease of habitats is fast, as occurred with the habitat destruction due to fish
introductions during the twentieth century in the Pyrenees (see above), there may be
a time lag before colonisation and extinction dynamics of the native species reach
equilibrium with current habitat distributions (defined as “non-equilibrium
dynamics” by Harrison 1991). As a result, species may persist for some time in
habitat networks, although they might go extinct some years later even without
further landscape change due to a time lag delay (defined as “extinction debt” by
Tilman et al. 1994). The apparent survival of species in networks that are insufficient for their long-term persistence may cause underestimates of the area and
quality of habitat needed to preserve threatened taxa (Hanski et al. 1996), and
overestimates of the species richness that landscapes can support in the long term
(Tilman et al. 1994). Therefore, the prevalence of nonequilibrium systems among
rare species or lineages, and the implications for their conservation need to be
determined as soon as possible (Bulman et al. 2007). However, urgent conservation
measures are needed, meanwhile these species-specific studies are not available.
8.6 Conservation and Restoration, What Has
Been Done so Far?
8.6.1 Protection Measures
Different initiatives have been implemented to stop species invasions at various
administrative scales. At European scale, the EU regulation 1141/2016 provides a
list of invasive alien species considered to be of Union concern (“the Union list”),
which does not include any fish species commonly used for stocking mountain
lakes. However the regulation contains an invitation for the Member States to
counteract the negative effects of some invasive alien species of national or regional
concern also cooperating at a regional scale (e.g. mountain ranges). The alien
invasive species of national or regional concern can be native in some European
Member States and, therefore, Member States could correctly undertake actions to
contrast all the species commonly used to stock mountain lakes. At present, there
8 Why Should We Preserve Fishless High Mountain Lakes?
195
can also be the case of other species with wider distribution, either because their
distribution is restricted to high mountain areas (fish introductions in mountain
areas are a global threat; Hulme et al. 2009) or because a synergy with other
stressors also affecting the remaining distribution area (e.g. Davis et al. 2010; Ban
et al. 2014; Matthaei et al. 2010). Recent genetic studies have also shown that for
other species with wide geographic distribution there are genetically differentiated
lineages in high mountain areas (Ventura et al. 2014; e.g. Bellati et al. 2014), that
might also be at risk of disappearance.
To what extent this substantial habitat loss is indeed affecting the survival of
some of the native species is not well known for most of them. Theoretical studies
point out that species-specific empirical studies are required with great urgency. If
the decrease of habitats is fast, as occurred with the habitat destruction due to fish
introductions during the twentieth century in the Pyrenees (see above), there may be
a time lag before colonisation and extinction dynamics of the native species reach
equilibrium with current habitat distributions (defined as “non-equilibrium
dynamics” by Harrison 1991). As a result, species may persist for some time in
habitat networks, although they might go extinct some years later even without
further landscape change due to a time lag delay (defined as “extinction debt” by
Tilman et al. 1994). The apparent survival of species in networks that are insufficient for their long-term persistence may cause underestimates of the area and
quality of habitat needed to preserve threatened taxa (Hanski et al. 1996), and
overestimates of the species richness that landscapes can support in the long term
(Tilman et al. 1994). Therefore, the prevalence of nonequilibrium systems among
rare species or lineages, and the implications for their conservation need to be
determined as soon as possible (Bulman et al. 2007). However, urgent conservation
measures are needed, meanwhile these species-specific studies are not available.
8.6 Conservation and Restoration, What Has
Been Done so Far?
8.6.1 Protection Measures
Different initiatives have been implemented to stop species invasions at various
administrative scales. At European scale, the EU regulation 1141/2016 provides a
list of invasive alien species considered to be of Union concern (“the Union list”),
which does not include any fish species commonly used for stocking mountain
lakes. However the regulation contains an invitation for the Member States to
counteract the negative effects of some invasive alien species of national or regional
concern also cooperating at a regional scale (e.g. mountain ranges). The alien
invasive species of national or regional concern can be native in some European
Member States and, therefore, Member States could correctly undertake actions to
contrast all the species commonly used to stock mountain lakes. At present, there
8 Why Should We Preserve Fishless High Mountain Lakes?
195